a(n) = 301*binomial(n-1,8)+52*binomial(n-1,7)+binomial(n-1,6).

Terms

a(0) =0a(1) =0a(2) =1a(3) =59a(4) =745a(5) =4665a(6) =19995a(7) =67287a(8) =191103a(9) =478335a(10) =1085370a(11) =2276560a(12) =4476758a(13) =8340982a(14) =14844570a(15) =25397490a(16) =41986770a(17) =67351314a(18) =105193671a(19) =160433625a(20) =239508775a(21) =350727575a(22) =504680605a(23) =714716145a(24) =997486425a(25) =1373571225a(26) =1868185800a(27) =2511980406a(28) =3341939004